U.S. Secretary of State Hillary Clinton, right, meets with the head of the Organization of the Islamic Conference, Ekmeleddin Ihsanoglu, left, in Jeddah, Saudi Arabia, on Tuesday. (Saudi Press Agency/Associated Press)

If Iran gets a nuclear weapon it could trigger a nuclear arms race in the Middle East, U.S. Secretary of State Hillary Clinton said Tuesday.

Clinton, speaking at a women's college in Saudi Arabia, told an audience of students that Iran's secret construction of a uranium enrichment facility near the city of Qom was an example of how Iran had violated its obligations to not pursue nuclear weapons.

"You have to ask yourself, 'Why are they doing this?' " Clinton said.

Clinton's statement comes a day after she told an audience in Qatar that Iran was moving towards a "military dictatorship" and said Iran's religious and political leaders were being “supplanted” by the Republican Guard Corps.

Iranian President Mahmoud Ahmadinejad brushed off Clinton's criticism, which he characterized as "not wise."

"We don't take her comments seriously," Ahmadinejad told a televised news conference Tuesday to announce that his country is installing more advanced centrifuges at a key nuclear facility.

Russia joins U.S., France in condemning Iran

Iran began enriching low-grade uranium to a higher level last week, a move that angered the United States and its Western allies, who called for another round of sanctions against the Islamic Republic. Iran is already subject to three rounds of UN sanctions

Ahmadinejad said at a news conference in Tehran the new centrifuges are not yet functioning, but he claimed they are five times more efficient than an older model at the Natanz enrichment facility.

While Iran has said the enrichment program is for its planned nuclear energy program, some countries believe it is trying to develop nuclear weapons.

In a letter to the head of the International Atomic Energy Agency made public Tuesday, the United States, France and Russia expressed their opposition to Iran's nuclear program. They also questioned Iran's statements that the enriched uranium is for fuel to power a research reactor to produce medical isotopes.

"If Iran goes ahead with this escalation, it would raise fresh concerns about Iran's nuclear intentions, in light of the fact that Iran cannot produce the needed nuclear fuel in time" to refuel the research reactor, the three governments said in their letter to the IAEA.

Clinton went further on Tuesday, saying Iran's program threatens to dash hope of a nuclear-free Middle East.

"If Iran gets a nuclear weapon, that hope disappears," she said, "because then other countries which feel threatened by Iran will say to themselves, 'If Iran has a nuclear weapon, I better get one, too, in order to protect my people.' "

One student attending Clinton's appearance at Dar al-Hekma college in Jeddah expressed disappointment that Clinton did not address Israel when discussing countries that should give up nuclear weapons. Israel has neither confirmed nor denied it has nuclear weapons, but is widely believed to have a small number in its arsenal.

Dalai M. Khayat told The Associated Press Clinton's response to a direct question on Israel "was not fulfilling."

With files from The Associated Press